The Histone Chaperone Facilitates Chromatin Transcription (FACT) Protein Maintains Normal Replication Fork Rates

Abstract

Ordered nucleosome disassembly and reassembly are required for eukaryotic DNA replication. The facilitates chromatin transcription (FACT) complex, a histone chaperone comprising Spt16 and SSRP1, is involved in DNA replication as well as transcription. FACT associates with the MCM helicase, which is involved in DNA replication initiation and elongation. Although the FACT-MCM complex is reported to regulate DNA replication initiation, its functional role in DNA replication elongation remains elusive. To elucidate the functional role of FACT in replication fork progression during DNA elongation in the cells, we generated and analyzed conditional SSRP1 gene knock-out chicken (Gallus gallus) DT40 cells. SSRP1-depleted cells ceased to grow and exhibited a delay in S-phase cell cycle progression, although SSRP1 depletion did not affect the level of chromatin-bound DNA polymerase ␣ or nucleosome reassembly on daughter strands. The tracking length of newly synthesized DNA, but not origin firing, was reduced in SSRP1-depleted cells, suggesting that the S-phase cell cycle delay is mainly due to the inhibition of replication fork progression rather than to defects in the initiation of DNA replication in these cells. We discuss the mechanisms of how FACT promotes replication fork progression in the cells.

Ssrp1a controls organogenesis by promoting cell cycle progression and RNA synthesis

“…Moreover, because Ssrp1a 1-518 can replace Drosophila Ssrp, our data indicate that the C-terminal HMGB-domain is dispensable in vivo. This is consistent with similar observations in vitro (Abe et al, 2011), and the fact that the yeast homologue Pob3 lacking an endogenous HMGBdomain interacts with the HMGB proteins Nhp6a and Nph6b (Wittmeyer et al, 1999). Also, other proteins can compensate for their function, as yeast lacking both factors are viable (Costigan et al, 1994).…”

“…3I). This indicates that Ssrp1a is required for S phase progression during development, consistent with in vitro results reporting Ssrp1 functions in DNA elongation (Abe et al, 2011).…”

FACT Proteins, SUPT16H and SSRP1, Are Transcriptional Suppressors of HIV-1 and HTLV-1 That Facilitate Viral Latency

“…Further study of FACT proteins in human retroviral transcription, as well as more profound analysis of FACT-mediated transcriptional regulation at the genome-wide scale in retrovirus-infected cells, may help to unravel the complicated functions of FACT that could be modulated by viral components. In addition, FACT is also a multifunctional protein complex that regulates other cellular processes, such as DNA replication (62)(63)(64), DNA damage response (65,66), and cell cycle progression (67,68). Whether FACT-mediated nontranscriptional functions may affect HIV-1/HTLV-1 replication is unclear and requires further investigation.…”

The FACT complex interacts with the E3 ubiquitin ligase Psh1 to prevent ectopic localization of CENP-A

“…One important factor that influences chromatin structure is the FACT (facilitates chromatin transcription/ transactions) complex (Orphanides et al 1998;Reinberg and Sims 2006). FACT facilitates many chromatin-based processes, including transcription initiation, transcription elongation, and DNA replication and repair (Belotserkovskaya et al 2003;Biswas et al 2005;VanDemark et al 2006;Abe et al 2011;Dinant et al 2013). To promote these functions, FACT generates a more open chromatin configuration via multiple contacts with nucleosomes to allow polymerases to move through chromatin (Belotserkovskaya et al 2003;Rhoades et al 2004;Xin et al 2009;Winkler et al 2011).…”